This invention relates to the preparation of reaction products of alkylene oxides with alcohols and other organic compounds having an active hydrogen. More particularly, this invention is directed to a process for such preparation employing a particular bimetallic compound as catalyst.
A large variety of products useful, for instance, as surfactants, solvents, and chemical intermediates, are prepared by the addition reaction (alkoxylation reaction) of alkylene oxides with organic compounds having one or more active hydrogen atoms. As an example, particular mention may be made of the alcohol ethoxylates and alkyl-substituted phenol ethoxylates prepared by the reaction of ethylene oxide with aliphatic alcohols or substituted phenols of about 8 to 20 carbon atoms, which ethoxylates are common nonionic detergent components of commercial cleaning formulations for use in industry and in the home. An illustration of the preparation of such an aliphalic alcohol ethoxylate (represented by formula III below) by addition of a number (p) of ethylene oxide molecules (formula II) to a single alcohol molecule (formula I) is presented by the equation ##STR1##
Alkylene oxide addition reactions are known to be promoted by contact with a catalyst, conventionally a catalyst of either acidic or basic character. Recognized in the art as suitable basic catalysts are the soluble basic salts of the alkali metals of Group I of the Periodic Table, e.g., sodium, potassium, rubidium, and cesium, and the soluble basic salts of certain of the alkaline earth metals of Group II of the Periodic Table, e.g., calcium, strontium, and barium. Conventional acidic alkoxylation catalysts include, broadly, the Lewis acid or Friedel-Crafts catalysts. Specific examples of these catalysts are the fluorides, chlorides, and bromides of boron, antimony, tungsten, iron, nickel, zinc, tin, aluminum, titanium and molybdenum. The use of complexes of such halides with, for example, alcohols, ethers, carboxylic acids, and amines have also been reported. Still other examples of known acidic alkoxylation catalyts are sulfuric and phosphoric acids; the perchlorates of magnesium, calcium, manganese, nickel and zinc; metals oxalates, sulfates, phosphates, carboxylates and acetates; alkali metal fluoroborates, zinc titanate; and metal salts of benzene sulfonic acid.
In one important aspect, the present invention relates to an alkoxylation reaction catalyzed by certain bimetallic oxo compounds. Such substances have been known in the chemical arts. Description of these and related compounds are described, for instance, in U.S. Pat. No. 3,432,445, Belgian Pat. No. 680,456, U.S. Pat. Nos. 3,607,785 4,281,087, 4,419,482, and 3,576,762, and in the publication of Ph. Teyssie et al entitled "Catalysis with Soluble M--O--M'--O--M Bimetallic Oxides (Chemtech., Mar. 1977, p. 193). The bimetallic oxo compounds have not, however, been recognized as useful in promoting alkoxylation reactions.
In other aspects, the invention further involves the discovery of a process for the production of alkylene oxide adducts (alkoxylates) characterized by a narrow alkylene oxide adduct distribution. Alkylene oxide addition reactions are known to produce a product mixture of various alkoxylate molecules having a variety of alkylene oxide adducts, (oxyalkylene adducts), e.g., having different values for the adduct number p in formula III above. The adduct number is a factor which in many respects controls the properties of the alkoxylate molecule, and substantial effort is often devoted to tailoring the adduct number distribution of a given product mixture to its intended service. In certain preferred aspects, the present invention is a process characterized by enhanced selectivity for the preparation of alkoxylate mixtures in which a relatively large proportion of the alkoxylate molecules have a number (p) of alkylene oxide adducts that is within a relatively narrow range of values. It is known that alkoxylate products having such a narrow range distribution are preferred for use in detergent formulations (Great Britain Pat. No. 1,467,134; Derwent Publications Research Disclosure number 194,010). Narrow-range alkoxylates are also known to be particularly valuable as chemical intermediates in the synthesis of certain carboxyalkylated alkyl polyethers (U.S. Pat. No. 4,098,818) and of certain alkyl ether sulfates (Great Britain Pat. No. 1,553,561).
Attempts made in the prior art to produce alkoxylates having a more narrow-range distribution of alkylene oxide adducts have centered upon processes for the preparation of alcohol alkoxylates, and most particularly upon the preparation of ethylene oxide adducts of higher (C.sub.8 to C.sub.20) aliphatic primary alcohols. The common conventional basic catalysts, i.e., compounds of the alkali metals, are known to be responsible for the production of alcohol ethoxylates having a relatively broad distribution. Conventional acid-catalyzed alkoxylation catalysts have long been recognized to produce alcohol ethoxylate products having a narrow distribution of alkylene oxide adducts. However, acid catalysis is known to have substantial disadvantage in several respects. For instance, the acids are often unstable, with limited life and effectiveness as catalysts in the ethoxylation mixture. Both the catalysts themselves and their decomposition products catalyze side reactions producing relatively large amounts of polyethylene glycols, and also react directly with the components of the alkoxylation mixture to yield organic derivatives of the acids. Overall, use of acid ethoxylation catalysts is known to result in relatively poor quality products.
A great deal of attention has recently been given in the art to processes which utilize basic compounds of the alkaline earth metals as catalysts for the preparation of alcohol alkoxylate products having a relatively narrow-range distribution. For instance, it has recently been reported (U.S. Pat. Nos. 4,210,764, 4,223,164, 4,239,917, 4,453,022, 4,453,023, 4,302,613, and 4,375,564 and the published European Patent Applications Ser. Nos. 0026544, 0026546, 0026547, 0085167 and 0092256) that alkoxylation promoted by basic barium, strontium, calcium and magnesium compounds, either alone or with specified co-catalysts, yields an alkoxylate having a distribution which is more narrow or peaked than that of the product of an alkoxylation promoted by basic compounds of the Group I metals. Such products are still, however, considered to be less than optimal from the standpoint of overall product quality, requirements for catalyst removal, and/or narrowness of product distribution.
Other recent disclosures of related alkoxylation processes include U.S. Pat. No. 4,456,697, which reports the use of a catalyst combining HF and a metal or mixed metal alkoxide of the formula M(OC.sub.n H.sub.2n+1)q wherein M is selected from the group consisting of aluminum, gallium, indium, thallium, zirconium, hafnium, and titanium as well as U.S. Pat. No. 4,375,564 which describes catalysts combining a magnesium compound with a compound of an element selected from the group consisting of aluminum, boron, zinc, titanium, silicon, molybdenum, vanadium, gallium, germanium, yttrium, zirconium, niobium, cadmium, indium, tin, antimony, tungsten, hafnium, tantalum, thallium, lead, and bismuth.